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[827/0] E. obscura... het vervolg from jonas on 2013-07-10 14:18:02.535388+02 -
This weekend I was in the haute fagnes and de Gaume with Elias de Bree. Quick summary.
- Eristalis alpina!
- three new km² for Eristalis obscura, in numbers! I think we can say we easily pick out the obscura's in the field! Much alike E. nemorum as said before.
- Chrysotoxum verralli
- Xylota ignava
- Blera
- Thyridanthrax fenestratus, Anthrax varius
- two new species for Belgium (TIpula trifascingulata and Agromyza archangelicae)
- and many many more!

Cheers
(ps: Rhingia rostrata reported in my previous message is in fact R. borealis. Not bad either)


[826/0] Eristalis obscura et al. from jonas on 2013-06-25 12:01:19.508746+02 -
Hi all,

besides our classic haute fagnes trips, we do have interest in the relatively unknown southern part of Belgium: 'de gaume'.
For butterflies it is a true hotspot, but also for other insects (eg grasshoppers) this is a nice area. I have never been here in spring, but its truly magnificent to watch flies!!!!

I visited the area by bike, for 3 days (14-15-16th of June). Most important findings:
- Microdon devius: at the known location, and a new location clearly linked to nest-bumps of Lasius niger!
- Paragus flammeus: abundant at one location
- Anasimyia lunulata: new locations
- Microdon myrmicae: new locations
- Chalcosyrphus valgus & Blera fallax: new locations
- Eristalis obscura (pseudorupium): found THREE males!!!! In 2010 Frank found this species in Belgium for the first time: in the haute fagnes, and he underligned the reduced wing markings. On the three males I found, the markings are reduced as well, and superficially, the species resembles E. nemorum!!! Accually: the species can be separated in the field rather quickly by the dark face (yellow in nemorum) and dark hairs on the back of F1. I caught 5 suspects, and 3 of them appeared to be E. obscura. In fact: there is another observation some 20 km away from mine, but I know for sure I cant 'publish' them here, so you will have to wait untill those pop up somewhere (...). Anyhow, it appears the species is strongly overlooked, and it might be quit dispersed in the region.
- Eristalis rupium
- Microdon cf mutabilis (did not find pupa... This is the giant from heathland, in contrary to the smaller ones from moist areas (myrmicae)).
- Brachyopa vittata
- Xanthogramma laetum
- Cheilosia ranunculi, pubera, nigripes, barbata,
- Rhingia rostrata
- Myolepta vara (my first: at last!!!)
- ...

To be continued :-)


[824/0] How to seperate panzeri from dorsata in the field? from Bastiaan on 2013-05-30 14:55:13.616207+02 -
Dear all,

last week, yes 1.5 days of sun! I went to check in all existing populations (Sphiximorpha subsessilis, Xantogramma leatum and B.dorsata) They where still there luckaly.
But during my walks I found also several Brachyopa panzeri on two still bleeding just cutted Fagus sylvatica (European Beech) trunks! So both species are in this area, no less than 1 km in distance from each other! That gave me the best opportunity to compare them better.

By using the key of Syrph the Net 2012 I found the best separation between them are the bristal colour of the hind margin of the scutellum. This character cannot be found in the Van Veen Key.

An other key character that cannot be found in both keys are the arista colouring: the arista in B.dorsata is almost black and in strong contrast with the 3rd antennal segment. The arista of B.panzeri is orange coloured all the way through.

Other character that I could not find in both keys are the darkened apical end of the vena spuria and wing tip in B.panzeri where B.dorsata does not have this.

The sensory pit characters are as in all keys correct but sometimes harder to see (depending on the correct viewing angle) especially in the field as of genital characters.

To sum up the new characters for field ID:

  • Scutellum hind margin with long black bristles (could be broken). Arista dark and in contrast with the 3rd antennal segment. No darker spots in the wing top or apical end of the vena spuria . -> B.dorsata

  • Scutellum hind margin without long black bristles (sometimes yellow bristles are present). Arista completely orange (no contract with 3rd antennal segment). Wing tip and apical end of the vena spuria darkened. ->B.panzeri
Hope this will add to a better separation between them in the field! Happy catching.

Cheers from rainy Brussels!

Bastiaan